Photosensitive discharge device



Oct. 19, 1948. E. n cARTHuR 2,451,850

PHOTOSENSITIVE DISCHARGE DEVICE Filed July 27, 1946 2 Sheets-Sheet 2 Fig.6.

Volts Inventor": ElmenDMAr-thun D #42447 His Attor-ney.

Patented Oct. 19, 1948 PHOTOSENSITIVE DISCHARGE DEVICE Elmer D. McAi-thur, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York Application July 27, 1946, Serial No. 686,668

Claims.

This invention relates to light-sensitive or photo-responsive electrical discharge devices, and more particularly to the type in which the lightsensitive or photo-responsive elements are combined within a single envelope in operative relation to a relatively more sensitive relay or amplifying means such as a grid-controlled discharge device particularly one of the type employing an ionizable medium.

While devices of the foregoing type have been known heretofore, the practical usefulness of the art has been limited by the lack of a device which is rugged in construction, simple to fabricate and capable of withstanding the adverse heating and like effects of the electric currents and potentials associated with the device. For example, one such effect which has heretofore caused considerable difficulty and delayed the development of a satisfactory device has been the destructive eifect on the light-sensitive or photo-responsive surface of heat from the heated cathode or the anode current of the relay discharge device associated therewith. Another has been the difiiculty in segregating, if and when desired, the light-induced currents and the elements associated therewith from the currents and associated elements of the relay or amplifying means.

It is the general object of my invention to provide a new and improved electric discharge device of the foregoing type which is rugged in construction, simple to fabricate, and which at the same time minimizes deleterious heating efiects on the light-sensitive or photo-sensitive surfaces.

It is still a further object of the invention to provide a new and improved discharge device of the foregoing type in which the photo-responsive elements are more efliciently segregated from the relay or amplifying means for the purposes of provricling more effective electrical and thermal insulation between the respective sets of elements.

Briefly stated, in the illustrative embodiments described herein, I accomplish the object of my invention by providing in one chamber of an envelope preferably containing an atmosphere of an ionizable medium, an electronic relay comprising a cathode, an anode and an electrostatic control member, while in a second chamber of said envelope I provide a photo-responsive means comprising a photo-emissive or light-sensitive member in operative relation to a photo-anode. The photo emissive member is electrically connected to the electrostatic control member of the first mentioned chamber while the photo-anode is connected to the cathode or anode. The configuration of all these elements is such that thermal effects of the thermionic cathode upon the photoemissive member are substantially minimized thereby appreciably diminishing deleterious effect upon the emission characteristics of that surface. At the same time the configuration permits of more effective additional cooling of the aforesaid surface by means of forced cooling methods such as cooled liquid currents or air circulation.

The features of the invention desired to be protected herein are pointed out in the appended claims. The invention itself, together with its further objects and advantages may best be understood by reference to the following description taken in conjunction with the accompanying drawings, in which Fig. 1 illustrates an embodiment of the invention in an electron discharge tube; Fig. 2 is a plan view taken along the line 2-2 of Fig. 1; Fig. 3 illustrates an alternative embodiment of the arrangement shown in Figs. 1 and 2; Fig. 4 is a plan view along the line 4--4 of Fig. 3; Fig. 5 illustrates schematically a circuit in which discharge devices embodying the invention may be employed, while Fig. 6 represents graphically certain operating characteristics of the circuit shown in Fig. 5. Throughout the drawings like numerals have been used to designate like parts.

The embodiment shown in Fig. 1 comprises an envelope l which is divided into two relatively thermally separated cylindrical chambers 2 and 3 by means of the transverse metallic wall 4 having external portions affording an externally accessible electrical contact which may be used as a terminal for internal electrodes. This division will facilitate the thermal insulation of the chambers 2 and 3 from each other as will be explained in greater detail hereinafter. The wall 4 is provided with 9. preferably circular aperture or opening 5 preferably positioned centrally or coaxially within envelope I.

The chamber 3 may be formed by any suitable construction which provides the wall 4. For example, it may be formed by a base 6 and a cupshaped member I which includes the wall 4 and a cylindrical wall portion 8 constituting an integral extension of the transverse wall 4. The chamber 2 may be formed by any suitable construction which provides a window portion 9 through which light or other electromagnetic wave energy may pass for the purpose of inducing photo-emissive activity in the elements hereinafter to be described. For example, it may be formed by an inverted cup-shaped member I 0 of glass hermetically sealed to the wall 4 by any of the glass-tometal sealing methods known in the art. Alterna- 3 tively, the glass portion of member l may extend only over the upper surface, the cylindical side wall ll being of metallic construction integral with the transverse wall 4. It will also be understood that the wall portion 8 of the cupshaped member I may be of insulating material such as glass.

Within the chamber 2 there is provided a photo-responsive discharge device including a photoanode' l2 and a photo-emissive member in the form of a frustroconlcal member l3 having a photo-emissive surface on its inner side and being conductively mounted upon the wall 4 concentribe welded to the wall 4 along the periphery of aperture 5 or connected thereto in any other suitable manner.

Within the chamber 3 there is provided an electric discharge device such as a grid controlled gaseous discharge tube, including the cathode l4, the grid I5 and the anode l6, all of which may be cylindrical in form and concentrically mounted with respect to each other by means of the insulating disk I! and the supporting rods l8 fix= edly attached to the disk i1 by means of ferrules l9. For purposes of clarity of the drawings, only four such rods have been shown. It will be understood, however, that any desired number necessary to afiord firm support may be used. Disk l1 maybe similarly mounted on base 6 by means of ferrules 20 and supporting rods 2|.

It will be observed that photo-anode I2 is supported by and constitutes a conductive extension of cathode l4. Similarly, the grid I5 is supported by and conductively connected to wall 4, as by welding thereto along the periphery of aperture 5. Thereby grid I5 is conductively connected to the photo-emissive member l3 through the aperture 5 and may be considered to be a conductive extension of member l3. By this construction, both grid IS-and member 13 are provided with an externally accessible terminal in the form of the outer portion of wall 4 or the wall portion 8.

'A suitable externally accessible terminal for the anode I6 is provided by the prong 22 hermetically sealed through the base 6 byvmeans of the glass bead 23 and conductively connected to the anode l6 by means of the lead connection 24. The lead connection 25 to the cathode I4 is similarly welded to an externally accessible prong 26 which is hermetically sealed through the base 6 by means of a similar glass bead (not shown). The cathode may be energized to provide thermionic emission by any of the well known types of cathode heaters such as the resistor heater 21 mounted within the cathode cylinder and energized by any'suitable source of current supplied 23 which are hermetically sealed through the base 6 in a manner similar to that of prongs 22 through leads 3!! and 3| and the prongs 28 and y cally with the aperture 5. The member i3 may and 26. For the purpose of orienting the prongs in conventional type sockets, the base may be provided with a key member 32 on the lower sur- 7 face thereof in the well known manner.

The envelope I will be hermetically sealed in the usual manner, such as by the glass bead 33 resting in the groove 34 of the base member 5 and hermetically sealing the lower edge of the microns or neon or xenon at suitable pressures. It will be understood that, alternatively the envelope may be completely evacuated, in which case the amplifier will operate as a vacuum-type triode.

It will be apparent that the chambers 2 and 3 provide a construction which facilitates thermal insulation of the photo-sensitive surface'of member l3 from the thermal efiects of the oathode l4, and other relatively hot members in chamber 3. The wall 4 being metallic will tend to conduct heat which might pass into chamber 2 to the external surfaces of the envelope. The efiect may be increased by cooling with air or liquid cooling means (not shown) those external surfaces such as wall portion 6. Additional insulating means may be provided by a collar 38 of asbestos or other thermally insulating material which encircles photo-anode l2 adjacent to its juncture with cathode i4 and completely fills the aperture 5. Collar 36 will tend to minimize convection which might tend to circulate thermal energy to chamber 2.

Referring now to Fig. 3, the embodiment there shown is identical in all respects with that of Fig. 1 except for the changed relative position of the cathode and anode of the discharge device in chamber 3. It will be noted that the anode now comprises the central member of the device and is shown as being formed of the rod 31 supported in a manner similar to that of the cathode sup port in Fig. 1 and constituting a conductive extension of the photo-anode H2. The cathode is shown as the member 38 eccentrically positioned with respect to the central portion of the chamber 3. The advantages of the construction are that the heated cathode is placed in a position such as will minimize further heat conduction to the upper chamber 2. Corresponding changes in the external terminal connections are made. The prong 22 is now connected to cathode 30 while prong 26 is connected to anode 31. As in Fig. 1, prongs 28 and 29 are connected to cathode heater 21.

From the foregoing it will be seen that I have I provided a light-sensitive discharge device which is rugged in construction, simple to fabricate, and,

which at the same time minimizes deleterious heating efiects on the photo-sensitive surface. It will also be apparent that my invention provides more eil'ective segregation of the voltages and currents of the amplifier in chamber 3 from the currents in the photo-responsive device in chamber 2. The photo-electrons from the photo-sensitive member i3 will for normal operating potentials be unable to traverse the transverse aperture 5 to become intermixed with the currents of the discharge device in chamber 3. Thus in the'arrangement of Fig. l, the photo-electrons will be confined to electrical association with only the cathode of the electrodes comprising the grid controlled discharge device; while in the arrangement of Fig. 3, they will be similarly confined to the electrical association with the anode of those electrodes.

In Fig. 5 there is shown an illustrative utilization circuit in which the device of Figs. 1 and 2 might find employment. The device is schematically indicated as the discharge device 39 comprising the anode 40, grid 4| and cathode 42 corresponding to the discharge device in chamber 3 of Fig. 1, and photo-anode 43 and photo-emissive member 44 corresponding to the photo-responsive device in chamber 2 of Fig. 1. For purposes of illustration it may be considered as being of the gaseous discharge type. The device may be energized by the transformer 45 comprising the secondary 46 and primary 41 connected to any suitable source of alternating current power (not shown). As indicated, the cathode 42 and the photo-anode 43 are connected to an intermediate point 48 on the primary 45, while the anode 40 and the grid 4| (together with the photo-emissive member 44) are connected to points on opposite sides of the point 48. For the purpose of providing a unidirectional bias for the grid 4| there is provided a variable resistor 49 shunted by a capacitor 50. As is well known in the art, the rectification of current flowing between the grid 4| and the cathode 42 during the portion of the cycle in which the grid is positively energized by the secondary 46, will establish a unidirectional negative bias across the resistor 49. In the circuit of the anode 49 there may be provided a suitable relay 5| comprising the solenoid -52 serially connected in the anode circuit and armature 53 arranged to contact a contact 54 when the solenoid is energized and a stop 55 when the solenoid is deenergized. Contacts 54 and armature 5| may be connected to any suitable utilization circuit (not shown) through the wire connections 59. A capacitor 51 may be provided for the purpose of filtering the solenoid current in a well known manner.

The circuit may be arranged to operate the relay 5| in response to a predetermined energy level in any suitable source of electromagnetic wave energy 58, which may be an incandescent lamp, an X-ray device, an ultraviolet light source or like source of rays capable of causing photoemission. The operation in this respect will be substantially as follows and reference may be made to the graphic curves of Fig. 6 for the purposes of illustration. The bias potential of the resistor 49 may be so adjusted that no current flows to the anode 40 in the absence of electromagnetic energy impinging on member 44 or in the presence of such energy below a predetermined intensity. The grid 4| may be represented as energized by the alternating potential of the left-hand portion of secondary 46 (curve 59 of Fig. 6) superimposed upon the bias potential indicated by the line 60. The anode 40 may be represented as energized by the alternating potential of curve 6| of Fig. 6. It will be understood that the alternating potential of the grid and that of the anode-will be displaced by 180 electrical degrees in phase relation. It now, photo-electric energy from the source 58 be caused to impinge upon the photo-emissive member 44, a positive potential in opposition to the bias of resistor 49 will thereby be imposed upon the grid 4| because of photo currents flowing between member 44 and photo-anode 43 through resistor 49 during that portion of the cycle in which grid 4| is negative in potential. If that positive potential is of sufllcient value the curves 59 and 69 will be raised to cause the anode 40 to draw current which may be of sufficient value to energize the relay 5|.

If the modification of Figs. 3 and 4 be employed in the circuit of Fig. 5, a similar result may be obtained. The photo-anode 43 will then be electrically connected to anode 40 and photocurrents flowing through resistor 49 during the positive half cycle of anode voltage will impose on grid 4| a positive potential in opposition to the bias of resistor 49.

It will be understood by those skilled in the art that the arrangement of the device 39 may be so 6 adjusted as to be responsive to any given intensity level of the electromagnetic wave energy emanating from the source It and impinging upon the photo-emissive member 44.

While I have shown and described particular embodiments of my invention, it will be obvious to those skilled in the art that various changes and modifications may be made without departing from my invention in its broader aspects and I, therefore, aim in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A photo-sensitive electric discharge device comprising an hermetically sealed envelope, a transverse metallic wall dividing said envelope into chambers disposed on opposite sides thereof, said wall having a portion external to said envelope, an aperture in said wall within said envelope, an electric discharge device comprising electrodes mounted within the chamber on one side of said wall including an anode, a cathode, and a control grid conductively connected to said wall, a photo-responsive discharge device comprising photo-responsive electrodes mounted within the chamber on the other side of said wall including a photo-emissive member and a photo-anode, and a window portion in said envelope operatively associated with said photo-emissive member, one of said photo-responsive electrodes being connected to said wall, the other through said aperture to one of said electrodes other than said grid whereby voltages between said photo-anode and said photoemissive member induced by photo-emission therebetween may be impressed between said electrodes, said portion of said wall constituting an externally accessible terminal for said control grid and said one of said photo-responsive electrodes and a heat dissipating surface for cooling said device.

2. A discharge device as in claim 1 in which said one of said photo-responsive electrodes is said photo-emissive member and the other is said photo-anode.

3. A discharge device as in claim 1 in which said one of said photo-responsive electrodes issaid photo-emissive member and the other is said photo-anode, said photo-anode constituting a conductive extension of said cathode through said aperture.

4. A discharge device as in claim in which said one of said photo-responsive electrodes is said photo-emissive member and the other is said photo-anode, said photo-anode constituting a conductive extension of said anode through said aperture.

5. A photo-sensitive electric discharge device comprising an hermetically sealed envelope, a transverse metallic wall dividing said envelope into chambers disposed on opposite sides thereof, said wall having a portion external to said envelope, a circular aperture in said wall within said envelope, an electric discharge device comprising electrodes within the chamber on one side of said wall including an anode, a cathode, and a cylindrical control grid conductively supported from said wall in coaxial alignment with said aperture, one of said electrodes other than said grid being mounted coaxially within said grid, a photo-responsive discharge device within the chamber on the other side of said wall comprising photo-responsive electrodes including a 7 frustro conical photo-emissive member conductively supported from said wall in coaxial alignment with said aperture and a photo-anode mounted coaxially within said photo-emissive member and constituting a conductive extension through said aperture of said one of said electrodes other than said grid, whereby voltages between said photo-anode and said photo-emissive member induced by photo-emission therebetween may be impressed between said electrodes. said portion of said wall constituting an externally accessible terminal for said control grid and said photo-emissive member and a heat dissipating surface for cooling said device, and a window portion in said envelope operatively associated with said photo-emissive member.

6. A device as in claim in which said one vof said electrodes other than said grid in said cathode and said anode comprises a cylindrical member mounted concentrically with respect to said grid.

7. A device as in claim 5 in which said one of said electrodes other than said grid is said anode.

8. A photo-sensitive electric discharge device comprising a cylindrical hermetically sealed envelope, a transverse metallic wall dividing said envelope into chambers disposed on opposite sides thereof, said envelope including a cupshaped transparent section sealed to one side of said wall and a cylindrical metallic section affixed to the other side of said well, a circular aperture in said wall within said envelope, an electric discharge device comprising electrodes within the chamber defined by said metallic section including an anode, a cathode, and a cylindrical control grid conductively supported from said wall in coaxial alignment with-said aperture, one of said electrodes other than said'grid being mounted coaxially within said grid, a photo-responsive discharge device within the chamber defined by said transparent section comprising photo-responsive electrodes including a frustro conical photo-emissive member conductively supported from said wall in coaxial alignment with said aperture and a photo-anode mounted coaxially within said photo-emissive member and constituting a conductive extension through said aperture of said one of said electrodes other than said grid, whereby voltages between said photoanode and said photo-emisslve member induced by photo-emission therebetween may be impressed between said electrodes, said cylindrical metallic section constituting an externally ac- 'cessible terminal for said control grid and said REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,709,763 Zworykin Apr. 16, 1929 1,821,808 Hull Sept. 1, 1931 1,883,926 Iams et al. Oct. 25, 1932 2,392,895 Adair Jan. 15, 1946 2,401,736 Janes June 11, 1946 

